Corn sugar syrups, made by acid hydrolysis of corn starch, are conventionally purified by treating them with strongly acidic, cation exchange resins containing sulfonic acid functional groups, followed by treatment with weakly basic resins made from styrenic, phenolic or epichlorohydrin-polyamine copolymers. These same cation exchange resins are used in the chromatographic and concentration of fructose in the corn sugar syrups. The relatively recent use of corn sugar syrup in the manufacture of carbonated soft-drink beverages has revealed the presence of an impurity in the syrup that reacts with soft-drink ingredients to form an objectionable haze in the beverage product. This haze-forming impurity has been traced to material extracted by the syrup from the sulfonic-group-bearing, cation exchange resins, and is present in syrups treated with such resins made both from styrenic and from phenolic copolymers.
Normal treatment of the corn sugar syrup includes an anion exchange step subsequent to the cation exchange step; this anion exchange step utilizes weakly basic anion exchange resins acceptable to the Food and Drug Administration for food applications. Such resins have been made from styrenic, phenolic and epichlorohydrin-polyamine copolymers. These resins remove a portion of the haze-forming impurity, called hereinafter "sulfonic resin extractables", but enough remains after typical treatment of the corn sugar syrup to produce a detectable, and therefore unacceptable, haze in the soft-drink product. The estimated level of sulfonic resin extractables forming this haze is about 0.1 to about 1 ppm of the sugar syrup. Attempts to remove this level of the impurity with activated charcoal have not been entirely successful.
During the preparation of "high-fructose" corn syrup (HFCS), the corn syrup product stream is separated chromatographically, using the sulfonic-groupbearing, cation exchange resins, into a concentrated fructose solution and a glucose solution. Commercial HFCS is produced by blending the concentrated fructose solution back into the corn syrup product stream to enrich the fructose level. As the individual, concentrated solutions and the enriched product stream have all been exposed to additional sulfonic-groupbearing, cation exchange resin, each will contain sulfonic resin extractables. This is especially significant where the chromatographic separation is not followed by other ion exchange treatments which are partially effective in removing the extractables.